HVdc

In the late 1880s, Thomas Edison was building a DC network in New York City to meet the needs of New Yorkers. The competing Tesla-Westinghouse AC system ultimately won the technology battle due to the invention of the AC transformer, which allowed large quantities of power to be efficiently transmitted from remote sites to communities all across North America. In the 1970s, new technologies in high-voltage, solid-state power electronics leveled the playing field, and DC became a viable choice for many markets worldwide.

Today, high-voltage direct current (HVDC) is at the forefront of America's emerging "smart grid" revolution and has emerged as an economically viable solution for long distance large power applications. HVDC is a perfect complement to the existing AC system for a number or reasons including:

HVDC cables keep energy losses to 3% per 1,000 km

Long underwater AC cables are impractical due to losses

HVDC cables generate virtually no electromagnetic fields

HVDC systems offer excellent (four-quadrant) control over power flows

Underwater routes minimize environmental impact

HVDC transmission has a high rate of availability and reliability

Underwater HVDC systems have extremely high reliability of service and are almost invulnerable to weather outage events